Normally I don't go too fast on the highway, 65 is generally around where I cruise at in the slow lane.

Well I was following one of my friends who was going a bit faster than that. At 70 I started feeling a vibration and it got really bad at 75, then it cleared up at around 80 mph. I felt the vibration through the steering wheel and through the gas pedal too.

Tonight I kinda noticed the same vibration at 55, then it cleared up at 65 mph.

I thought it was either my wheels might have become unbalanced, so I ran by NTB and they checked out all the wheels. One of the rears was out of balance, and a front was slightly bent. Thank god they're only stock wheels. I can double check to make sure it isn't one of the wheels when I throw my Telstars back on.

If that isn't it, is the next usual suspect the DS? I thought it might be that my stock springs or shocks are just gone, but dad came down and put some weight on them and they all seem fine.

Any ideas? Thanks! BTW, I've got poly motor and tranny mounts.

 

First, get properly balanced wheels tires on the car. If you still have the problem, move the front wheels to the back, back to the front (if same sizes) and check again. If the vibration still exists did it seem to move with the wheels? If so, you've got an out of balance wheel/tire. Having said that, it does kind of sound like the driveshaft, but I'd check the wheels/tires first.

 

Mine had the same issues. The high speed vibration was solved by installing an aluminum driveshaft. The low speed, 45-50mph, shaking was solved by jumping out the IAT with a 4.7k resistor.
Mine only used to shake at low speed when it was warm out.